This invention relates to communications networks, and specifically to a network which is suitable for home use, for the synchronization of distributed wired/wireless multimedia content to be played by multiple multimedia devices, e.g. monitors, audio systems, etc., and to a method for synchronizing wired and wireless output devices.
The prior art in this field is generally concerned with minimization of network latency. Most of the prior art relates to transmission of multimedia through wired networks, and does not consider that in wireless broadcast applications, imposition of delay through channel coding, or retransmit delay, is both feasible and necessary.
In known multi-stream multimedia play back systems, where the streams are output on different types of devices, playing the same set of streams on different output devices requires the use of a single transmission media. The use of different transmission media, which may include multiple hops over wireless media, as well as multiple hops over wired media, is not considered. The use of different transmission media may be of particular relevance to home and small office networks, where repeaters may be used to account for uncertain propagation conditions within the home/small office. The prior art does not consider networks in which a multimedia stream, because of quality-of-signal (QoS), or capacity limitations, may have different transmission rates at different points in the network. Furthermore, the use of wired/wireless media implies that different delays imposed by coding may be needed. The prior art does not consider networks in which multiple streams can arise from different physical locations in the network with different delays, which might occur within certain ad-hoc networks; and the prior art does not consider that a priori network information may be exploited so that new devices may xe2x80x9cjoinxe2x80x9d the network mid-transmission.
U.S. Pat. No. 5,617,539, for xe2x80x9cMultimedia collaboration system with separate data network and A/V network controlled by information transmitting on the data network,xe2x80x9d to Ludwig et al., granted Apr. 1, 1997, describes a system that integrates real-time and asynchronous networks. This system, however, does not address the wired/wireless synchronization issue, nor does it address the multi-hop wireless synchronization issue.
U.S. Pat. No. 5,623,483, for xe2x80x9cSynchronization System for Networked Multimedia Streams,xe2x80x9d to Agrawal et al., granted Apr. 22, 1997, discusses multi-stream multimedia content which is played on different output devices and how, with the use of buffers, two disparate multimedia streams may be synchronized to each other.
U.S. Pat. No. 5,689,641, for xe2x80x9cMultimedia collaboration system arrangement for routing compressed AV signal through a participant site without decompressing the AV signal,xe2x80x9d to Ludwig et al., granted Nov. 18, 1997, further describes the system of U.S. Pat. No. 5,617,539.
U.S. Pat. No. 5,790,792, for xe2x80x9cMethod and apparatus for transmitting multimedia from an application logic server to interactive multimedia workstations,xe2x80x9d to Dudgeon et al., granted Aug. 4, 1998, describes a network wherein a server handles all processing of real-time graphical images, however, this reference does not consider synchronization or wireless issues.
U.S. Pat. No. 5,754,241, for xe2x80x9cVideo decoder capable of controlling encoded video dat,xe2x80x9d to Okada et al., granted May 19, 1998, describes an MPEG decoder having an over-flow proof buffer.
U.S. Pat. No. 5,754,961, for xe2x80x9cRadio communication system including SDL having transmission rate of relatively high speed,xe2x80x9d to Serizawa et al., granted May 19, 1998, describes a system having both high and low speed transmission/reception capabilities.
U.S. Pat. No. 5,757,857, for xe2x80x9cHigh speed self-adjusting clock recovery circuit with frequency detection,xe2x80x9d to Buchwald, granted May 26, 1998, describes a circuit wherein all transmission is done without any systemic phase offset.
U.S. Pat. No. 5,758,079, for xe2x80x9cCall control in video conferencing allowing acceptance and identification of participants in a new incoming call during an active teleconference,xe2x80x9d to Ludwig et al., granted May 26, 1998, is related to U.S. Pat. No. 5,689,641, discussed above. This reference continues the discussion of synchronization of real-time and asynchronous networks, but still fails to address the issue of wired/wireless packet data synchronization.
U.S. Pat. No. 5,768,321, for xe2x80x9cAutomatic frequency control unit which detects a frame pattern in a phase modulation signal,xe2x80x9d to Watanabe et al., granted June 16, 1998, describes the transmission of a multimedia signal by a satellite communications system.
U.S. Pat. No. 5,777,612, for xe2x80x9cMultimedia dynamic synchronization system,xe2x80x9d to Kataoke, granted Jul. 7, 1998, describes a multimedia system which allows a user to output synchronized multimedia information starting at a point other than the beginning of a data stream.
U.S. Pat. No. 5,778,191, for xe2x80x9cMethod and device for error control of a macroblock-based video compression technique,xe2x80x9d to Levine et al., granted Jul. 7, 1998, describes application of a fixed length packet synchronization system to variable length data.
U.S. Pat. No. 5,790,533, for xe2x80x9cMethod and apparatus for adaptive RF power control of cable access units,xe2x80x9d to Burke et al., granted Aug. 4, 1998, describes the use of adaptive RF control of data transmission from a device, such as an A/V receiver, attached to a communications network.
U.S. Pat. No. 5,802,294, for xe2x80x9cTeleconferencing system in which location video mosaic generator sends combined local participants images to second location video mosaic generator for displaying combined images,xe2x80x9d to Ludwig et al., granted Sep. 1, 1998, is a continuation of U.S. Pat. No. 5,689,641, discussed above.
U.S. Pat. No. 5,809,075, for xe2x80x9cHigh speed communications system for analog subscriber connections,xe2x80x9d to Townshend, granted Sep. 15, 1998, describes a system using pulse code modulation to achieve relatively high transmission rates over conventional telephone lines.
U.S. Pat. No. 5,809,454, for xe2x80x9cAudio reproducing apparatus having voice speed converting function,xe2x80x9d to Okada et al., granted Sep. 15, 1998, describes a system for increasing the transmission rate of voice data, while maintaining the normal pitch of the speaker""s voice.
U.S. Pat. No. 5,815,634, for xe2x80x9cStream synchronization method and apparatus for MPEG playback system,xe2x80x9d to Daum et al., granted Sep. 29, 1998, describes a system for pausing or freeze-framing an audio visual presentation wherein the sound is muted when the picture is stopped, and wherein the sound and picture are substantially synchronized when playback resumes. This reference does not address the technology as applied to a wireless/wired interface.
U.S. Pat. No. 5,818,906, for xe2x80x9cConnection event reporting in a cable telephony system,xe2x80x9d to Grau et al., granted Oct. 6, 1998, describes a system wherein events which occur on the communication system are logged, and information about the type and frequency of connections made available for network management.
U.S. Pat. No. 5,828,866, for xe2x80x9cReal-time synchronization of concurrent views among a plurality of existing applications,xe2x80x9d to Hao, et al., granted Oct. 27, 1998, describes a system for synchronizing multiple applications located and operating on multiple processors.
U.S. Pat. No. 5,832,088, for xe2x80x9cMethod and apparatus for preventing data copying from a disk using data lengths too large for a pirate medium,xe2x80x9d to Nakajima et al., granted Nov. 3, 1998 describes a system for preventing the recording of data by an unauthorized entity.
U.S. Pat. No. 5,832,218, for xe2x80x9cClient/server electronic mail system for providing off-line client utilization and seamless server resynchronization,xe2x80x9d to Gibbs et al., granted Nov. 3, 1998, describes a system for synchronizing an EMail server to a client.
U.S. Pat. No. 5,841,482, for xe2x80x9cTransition aligned video synchronization system,xe2x80x9d to Wang et al., granted Nov. 24, 1998, describes the insertion of delay signals into an A/V 20 signal without the use of a phase locked loop.
U.S. Pat. No. 5,854,799, for xe2x80x9cVideo decoder with functions to detect and process errors in encoded video data,xe2x80x9d to Okada et al., granted Dec. 29, 1998, describes the replacement of an error-carrying macroblock with an error-free macroblock from a previous frame.
U.S. Pat. No. 5,854,893, for xe2x80x9cSystem for teleconferencing in which collaboration types and participants by names or icons are selected by a participant of the teleconference,xe2x80x9d to Ludwig et al., granted Dec. 29, 1998, is a continuation of U.S. Pat. No. 5,689,641, discussed above, and relates to a teleconferencing system wherein the current participants control entry of new participants into the conference.
U.S. Pat. No. 5,857,201, for xe2x80x9cEnterprise connectivity to handheld devices,xe2x80x9d to Wright, Jr. et al., granted Jan. 5, 1999, describes a system wherein a variety of devices may be connected to a central server regardless of the devices"" operating system.
U.S. Pat. No. 5,862,451, for xe2x80x9cChannel quality management in a cable telephony system,xe2x80x9d to Grau et al., granted Jan. 19, 1999, describes a system wherein, upon initiation of a link by a user, and upon location of a busy channel that the link is intended to traverse, an idle channel is queried to determine if the idle channel is of sufficient quality to complete the link.
U.S. Pat. No. 5,867,654, for xe2x80x9cTwo monitor videoconferencing hardware,xe2x80x9d to Ludwig et al., granted Feb. 2, 1999, is related to U.S. Pat. No. 5,689,641, and describes the use of two monitors in a videoconferencing system.
U.S. Pat. No. 5,884,039, for xe2x80x9cSystem for providing a directory of AV devices and capabilities and call processing such that each participant participates to the extent of capabilities available,xe2x80x9d to Ludwig et al., granted Mar. 16, 1999, is related to U.S. Pat. No. 5,689,641, and describes limiting the implementation to a least common denominator.
U.S. Pat. No. 5,886,734, for xe2x80x9cApparatus and method for storage and playback of video images and audio messages in multipoint videoconferencing,xe2x80x9d to Ozone et al., granted Mar. 23, 1999, describes a video conferencing xe2x80x9choldxe2x80x9d button. The reference does not address the issue of wireless/wired networks.
A system for synchronizing a multimedia content stream signal, emanating from at least one multimedia source, for play through a plurality of output devices, wherein the output devices are connected to the multimedia source by wired connections and wireless connections; the system including plural output realms, including wired realms and wireless realms; and which includes delay synchronizers and for determining a buffer delay for streaming the multimedia content stream signal from a buffer to an output device. A method of synchronizing a multimedia content stream for output to a plurality of wired and wireless output device in a network having plural realms, wherein each realm includes a CTL, includes buffering the multimedia content stream in a first realm; determining a buffer delay; transmitting the buffer delay to all CTLs in all realms of the network; and transmitting the multimedia content stream to all realms in the network.
An object of the invention is to provide a system and method for integrating a wired and wireless multimedia network.
Another object of the invention is to provide for the synchronization of a multistream, multimedia network.
A further object of the invention is to provide a system and method for determining a buffer, or synchronization, delay to synchronize a multimedia content stream output from a plurality of wired and wireless output devices.